In recent years, in a device which transmits a signal using light, such as a light coupling element or a light data link, characteristics such as a light emitting efficiency of a light emitting element have improved, and transmission loss of plastic light fiber, which forms a light transmission line, also has been decreased. For this reason, such a device makes it possible to perform high capacity and low cost light data communication. In such light data communication environment, it is necessary to increase the dynamic range of a light receiving circuit and to maintain stable operation over a wide operation range.
As transmission distance of a light transmission line increases, the strength of a light signal to be transmitted ranges from a very low level to a very high level, so that increasing the dynamic range of a light receiving circuit poses a serious problem. For example, in a light receiving circuit that includes a light receiving element and a trans-impedance amplifier (TIA) at an input stage, if a very low level light signal is received, the gain of the trans-impedance amplifier may be set accordingly, but if signal strength is also strong (or becomes strong), the trans-impedance amplifier becomes saturated, and oscillation may occur. Thus, it is difficult to expand a dynamic range of a light receiving circuit.